1. Technical Field
The technical field relates to an optical element driving device for driving an optical element of an imaging apparatus, and to an imaging apparatus in which this device is used.
2. Description of the Related Art
Recent years have witnessed the practical application of products such as digital imaging apparatus, typified by digital still cameras and digital video cameras, which are equipped with image blur correction mechanisms that correct image blur caused by hand shake in the pitch and yaw directions of the apparatus during image capture. With most image blur correction mechanisms, image blur is corrected by using a lens driving device (an example of an optical element driving device) to drive part of the imaging optical system in two directions, namely, a pitch correction direction and a yaw correction direction that are perpendicular to the optical axis.
Furthermore, lens driving devices for correcting image blur are increasingly being installed in imaging apparatus that make use of a bending optical system including prisms, mirrors, and so forth.
An advantage of an imaging apparatus equipped with a bending optical system is that the camera main body can be thinner. Accordingly, the lens driving device for correcting image blur also needs to be thinner in the thickness direction of the camera main body, which is accomplished, for example, by disposing the linear actuator or other drive unit on one or both sides with respect to the lens. For instance, imaging apparatus are known in the past in which the drive unit is provided on one or both sides of the lens and the camera main body is made thinner in its thickness direction, as disclosed in Japanese Laid-Open Patent Applications 2006-243704, 2007-17957, and 2000-194027.
With the lens driving device disclosed in Japanese Laid-Open Patent Application 2006-243704, two drive units for driving in the pitch and yaw correction directions are provided on one side in the yaw correction direction of a circular lens (an optical element), and disposed to be spaced apart vertically. The elliptical coil and magnets that constitute the drive units are disposed above and below on one side of the lens. The coils are disposed such that they are wound around an axis perpendicular to the optical axis.
With the lens driving device disclosed in Japanese Laid-Open Patent Application 2007-17957, the correcting lens is roughly elliptical in shape, obtained by cutting off two circular sides in parallel. The major axis direction of this lens is termed the yaw correction direction, and two drive units for driving in the pitch and yaw correction directions are disposed on one side in the yaw correction direction, and aligned vertically. The coils are disposed such that they are wound around an axis parallel to the optical axis.
With the lens driving device disclosed in Japanese Laid-Open Patent Application 2000-194027, a pair of drive units for driving in the pitch correction direction and a pair of drive units for driving in the yaw correction direction are disposed on both sides in the lengthwise and lateral directions of a circular lens to surround the lens on four sides.
With these three patent documents, a guide unit having a guide shaft is used to guide in the pitch correction direction and the yaw correction direction, and the lens is guided linearly by a bi-directional guide shaft.
With the lens driving devices discussed in Japanese Laid-Open Patent Applications 2006-243704 and 2007-17957, first and second direction drive mechanisms are disposed on one side of the lens, so no drive mechanism needs to be disposed in the thickness direction, which allows the camera main body to be thinner. However, since drive force is imparted to one side of the lens that is driven, the drive center of the drive mechanisms ends up being separated from the movable center of gravity of the portion that moves. Therefore, rotational moment is generated in the moving portion, the drive direction is at an angle to the movement direction with the guide shaft that linearly guides the lens, and a jerky motion tends to result from an increase in sliding resistance. Consequently, the lens driving devices discussed in Patent Documents 1 and 2 tend not to drive the lens accurately.
With the lens driving device discussed in Japanese Laid-Open Patent Application 2000-194027, the lens can be driven relatively accurately because both sides of the lens are driven uniformly. However, since pairs of drive units of the lens driving device are disposed to surround the lens on four sides, the size of the lens driving device increases in the thickness direction of the camera main body, so it is more difficult to reduce the thickness of the camera main body.